Mass transfer in back arc basin hydrothermal system was investigated. Mariana back arc basin hydrothermal are deposits, Kuroko deposits in Japan and hydrothermally altered rocks in the Kuroko area were studied in detail. Analytical results of hydrothermally altened rocks in the Kuroko area show the alteration trend similar to those in the ridge system. Rare earth elements pattern and distribution and chemistry of alteration minerals provide constraints on the evolution of hydrothermal system.